Sorry, the first two morphemes are derived from the second person plural possessive. I assumed an analysis where the root is *izw (corresponding to modern igg(e)) and *-er (corresponding to modern -(e)r) is suffixed to some pronouns to derive possessive forms. These are the morphemes that have already been guessed. Sorry for being unclear about that.

Sorry, the first two morphemes are derived from the second person plural possessive. I assumed an analysis where the root is *izw (corresponding to modern igg(e)) and *-er (corresponding to modern -(e)r) is suffixed to some pronouns to derive possessive forms. These are the morphemes that have already been guessed. Sorry for being unclear about that.

Oh, that's OK. Thanks for clarifying. Is the third morpheme an inflectional/agreement suffix?

Sorry, the first two morphemes are derived from the second person plural possessive. I assumed an analysis where the root is *izw (corresponding to modern igg(e)) and *-er (corresponding to modern -(e)r) is suffixed to some pronouns to derive possessive forms. These are the morphemes that have already been guessed. Sorry for being unclear about that.

Oh, that's OK. Thanks for clarifying. Is the third morpheme an inflectional/agreement suffix?

Yes
I think it's fair to declare you the winner right now. It is the second person plural possessive pronouns with agreement for plural/non-singular number and dative case. And for all your suffering here is a reward: An example sentence.